Method of preparing intaglio lithographic plates from original plates and transfers



Feb. 26, 1935. R F, REED E1- AL 1,992,771 METHOD oF PREPARING INTAGLIo LITHOGRAPHIC PLATES FROM ORIGINAL PLATES AND TRANSFERS Filed Nov. 28, 1955 l NV EN T0125.

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Patented Feb. 26, 1935 vUNITE-D lSTATES PATENT OFFICE nm'rnon or mesma m'rAauo Limcanarino m'ras non calamar. m'ras AND 'rmsraas Appueauon November as, 193s, serial No. 700,114

claima.

.This invention relates to a method of preparing deep-etched or intaglio lithographie plates from original plates and transfers. As is well known in the art, lithographie plates having the design 5 areas etched slightly below the non-.printing areas may be prepared by the general method of coating the plate with a. light-sensitive bichromated co1- loid, exposing it to light in contact with a photographic positive, dissolving the unhardened colloid from the design areas of the plate with water or other developing solution, etching the design areas slightly intaglio, depositing ink or an ink-receptive substance on the clean metal surfaces constituting the design area, and finally 5 removing the light-hardened colloid coating from the non-printing areas. Efforts have also been made to prepare similarly deep-etched or intaglio lithographie plates from plates upon which the work has been drawn with crayon, tusche or 0 lithographie writing ink or produced by means of hand transfers. These eiorts however have not met with widespread success.

The object of this invention is to providea method of preparing plates of this type suitable for use in the present day commercial lithographing plants. The steps in preparing plates of the type in question are as follows: y

1. 'I'he designds produced upon the plate in greasy ink or crayon.

2. The plate including the design areas is coated with a powder adapted to increase the wetting action of a solution of a bichromated colloid.

3. The entire plate is coated with a solution containing a bichromated colloid.

4. The bichromated colloid is hardened by exposure to light.

5. The bichromated colloid and greasy ink are removed from the image areas.

6. The printing areas of the plate are etched o slightly intaglio with an etching medium which does not attack the colloid overlying the non-design areas.

'7. An ink receptive substance is deposited upon the design areas of the plate. 45 8. The bichromated colloid or etching resist is removed from the non-design areas. f

While this series of steps summarizes the process constituting this invention, particular attention must be paid to certain important factors involved in several of the individual steps.

After the greasy printing image has been deposited upon the plate it isl necessary to coat the entire plate with a material capable of forming an etching resist. A lithographie plate having a 55 greasy design thereon presents a surface for coating that does not permit a free flow of coating solution in all directions under ordinary conditions. If coated by whirling, streaks are produced radiating from the center of rotation, by the interierence of the greasy design areas with viiow (Cl. irl-41.5)

of the coating solution. If the coating is done by hand as in the usual procedure of gumming up a plate, it is found that, around the boundaries 'of the greasy design areas, the coating is thinner than in the larger open areas and there is great diiilculty in producing a coating suiilciently thick and uniform to serve as an eiective etching resist.

We have found that, in a successful method of preparing .deep etched plates from originals orY transfers, it is necessary that the resist be capable of flowing evenly over, and coating uniformly, the greasy design areas and the non-printing areas of the plate alike. A suitable method of accomplishing this is to'dust the plate with a dry powder such as rosin, asphaltum, starch, flour, talc or a mixture of two or more powders capable of adhering to the inked .areas which constitute the design, and of producing capillary activity suilicient to permit free flow of the coating solution thereon.

Another point of great importance is the thick-` ness of the nlm of acid resisting material. If this film be not thick enough there is a tendency for the etching acid to penetrate it and attack the non-printing areas of the plate. We have found that this drawback is overcome by using a coating solution containing more than 12 grams solids per 100 cc. and preferably about 20 grams solids per 100 cc., Athe exact concentration depending upon the grain of the plate and the whirler speed.

The coating solution iuld contain one or more proteins, such as ilsh glue, animal glue or albumin in combination with a bichromate. In our process we prefer a coating solution of the following composition:

Parts by weight Albumen (flakes) 1 Photo-engravers glue (50% solids) 2 Ammonium bichromate 0.6

Water, suillcient to make a solution containing 20 grams total solids per 100 cc.

Good results, however, may be obtained with other proportions of the two colloids and our claims are not limited to the example given.

When the plate is coated as described above, the light-sensitive film will vary in thiclmess, being thicker at the boundaries of the design areas than on either the design areas or nondesign areas.

The light exposure suiilcient to insolubilize the bichromate colloid lm of the usual thickness is insuiiicient to insolubilize the thicker coating existing at the design-boundaries, through its entire thickness and consequently, when the ink is removed subsequently from the design areas by means of water and an ink solvent the colloid nlm strips from the metal surface inthe neigh. borhood of the design'and leaves the boundaries of the design without an effective resist during the subsequent etching. This results in ragged andl poorly denned design boundaries on the finished plate.' We have found that it is necessary. therefore, to increase the light exposure of the bichromate-colloid film suillciently to insolubilize those parts adjacent to -the design boundaries. The exposure necessary to accomplish this end 'is two or more times the exposure suillcient'to insolubilize the colloid illm not lying adjacent to disadvantage that they rapidly attack and de-v stroy the grain of zinc plates, reducing ltheir water holding capacity, and also thatI they tend to break through the ink and attack the design' areas. Y Solutions of alkali metal hydroxides possess th disadvantages that (1) they rapidly attack and corrode the. skin of operators and (2) they sa-` ponify and dissolve any fatty components of the ink or ink-receptive substance overlying the design. We have overcome these disadvantages by using as a remover of the bichromate-colloid film, a solution of an alkaline earth hydroxide 'or a mixture of an alkaline earth hydroxide and an alkaline earth salt. Such a solution. does not attack the surface of zinc plates or stones, or damage the grain thereof; itis very much less corrosive'to the skin oi! operators than solutions of valkali metal hydroxides; it does not remove the fatty components of the ink which overlies the. design areas. d To prepare a deep-etched or intaglio lithographic plata-we proceed as follows:

. image is produced on a clean, grained zin platebyfany means in which a' greasy ink or crayon is applied directly to the'metal surface, such las transferring or crayon drawingk and said image is worked up in greasy ink by methods known to the art, The greasyima'ge is then dusted first with' powdered rosin and afterward v with powdered'talc to make the surface more easily wet by water soltions.V 'I'he plate then washed with waterto remove excess rosin and talc. When the excess water has been removed -but before the plate dries, it is coated with a bichromate-colloid solution preferably having the following composition:

- vParts by weight Photo-'engravers glue'(50% solids) 2 Albumen (dried)' f' 1 Ammonium bichromate 0.6

Water, sumcientto make a solution containing 20 grams total solids per 100 cc.

In order that the present invention may be better understood, reference is made to the accompanyingdrawing wherein:

Figure 1 is a -atic elevation in section on an enlarged scale of a metal plate whereon a design has been deposited by means of greasy inkorcrayon.

Figure 2 is'a corresponding view showing the inked design -on the metal plate covered by a rosin or talc dust.

Figure 3 is acorresponding viewshowing the plate after the application 'of the light-sensitive colloid coating.

Figure 4 shows'the plate after the colloid coating has been exposed to light.

Figure 5 shows the plate after the inked design has been removed from the plate. A

Figure 6 shows the plate after etching.

Figure 7 shows the plate after an ink coating has been applied after an asphaltum wash.

Figure 8 shows the plate in final form after reimoval of the colloid lm.

'I'he plate is whirled to distribute the coating uniformly and allowed to dry. The coated plate is next exposed to the light of an arc lamp for a period two or moretimes as long as is necessary to insolubilize the colloid lm not adjacent to the design boundaries. After exposure the plate is washed with water, the excess water removed and,

while damp, the plate is washed with a solvent for ink,such as gasoline or benzine, and rubbed gently with a cotton wad to remove the inkand its overlying nlm of hardened colloid. The image thus prepared is etched with a solution of' an acid or salt in practically anhydrous alcohol. Acids and salts such as hydrochloric, nitric and sulphuric acid, ferrie chloride, and others, are suitable for this purpose but we prefer an etch of the following composition: 1

Hydroemoric acid, awa-38.5% sec. Anhydrous alcohol 95 cc.

fully so long as they are practically anhydrous. After etching, the plate iswashed with anhy drous'alcohol, gasoline or turpentine, using a wad of cotton and suillcient abrasion lto dislodge the residue from the etched areas, after which the vplatefls dried. 'I'he`plate :is then coated with a solution of asphaltum or any one of the commonly l used wssnrout'soluuons, and dried, after which it is again coated with `liquid developing ink, or with a lithographic'ink thinnedwith a solvent such as turpentine, to render the etched design greasy or grease-receptive. It is then dusted with powdered talc to render the plate surface wettable by water. The plate is then treated with a solution of the following composition:

v, Grams Barium chloride 8 sodiumhydroxide 1 Water, suilicient to make a total volume of This solution is distributed over the surface, at the same time rubbingwith a wad of the colloid film is removed. The plate may or may not be counter-etched at this point by nowing with' hydrochloric acid solution containing one part of 37% hydrochloric acidin 200 parts of water, but in either case it is then desensitized and rolled upJn the known manner of preparing transfers or original plates for the press.

Claims directed to the use of barium chloride and barium hydroxide fo'r removing bichromated lms from lithographic plates are reserved forour co-pending application Serial Number 700,115.

cotton until' Having described our invention, we'desire to be limited only by the following claims:

1. A process of preparing deep-etched or intaglio lithographic plates from original plates or transfers, comprising, powdering the inked design to render it wettable, coating the entire plate with a solution of a light-sensitive bichromated protein or mixture of proteins containing more than 12 grams solids per 1GO cc. of solution, exposing to light ifor more than double the time necessary to insolubilize the coating, removing ink from the image with an ink solvent in the presence of moisture, etching the design slightly intaglio, depositing on the design a greasy or grease-receptive ground, and removing the resist by means of a solution containing an alkaline earth hydroxide.

2. A process of preparing deep-etched or intaglio lithographic plates from original plates or transfers, comprising powdering the inked design to render it wettable, coating the entire yplate with a solution of a light-sensitive `bichromated protein or mixture of proteins containing more than 12 grams solids per 100 cc. of solution, exposing to light for more than double the time necessary to insolubilize the coating, removing ink from the image with an ink solvent in the presence of moisture, etching the design slightly intaglio, depositing on the design a greasy or grease-receptive ground, and removing the resist by means of a mixture of an alkaline earth hydroxide and an alkaline earth salt.A

3. A process of preparing deep-etched or intaglio lithographic plates from original plates or transfers in which the following steps are used: dusting the inked design to render it wettable by the bichromate-colloid coating solution; coating the entire surface with a bichromatecolloid solution containing more than 12 grams of solids per 100 cc. of solution; exposing vthe bichromate-colloid coating to'light for two or more times the time necessary to insolubilze the coating removing "the light-hardened colloid coating from the design area; and after etching and inking the design removing the bichromate-y colloid coating with asolutioncontaining an alkalineearth hydroxide.`l l f' .A 4. A process of preparing deep-.etched or intaglio lithographic plates from'4 original plates or- `transfers in which the following steps are jused: dusting the inked design to render it -wettable by the bichromate-collold "coating solution; `:coat-g ing the entire surfacewith'a bichromate-colloid solution containing more than 12 grams offsolids per 100 cc. of solution; exposing the bichromatecolloidv vcoating. to light `for two or more times the time necessary to insolubilize the coating removing the light-hardened colloid coating from the vdesign* area; andl after etching Vand the design, removing the r4biehroinate'-colloid` coating with' a solution containing amixture of an alkaline earth 'hydroxide and;,analkalinev earth chloride.

5. A process of preparing intaglio lithographic plates from original plates or transfers, comprising, coating the entire plate with a solution of a light-sensitive bichromated colloid, light-hardening the bichromated colloid over the surface of the entire plate, removing the ink and the light-hardened colloid overlying it from the printing areas of the plate by abrasion in the presence of moisture and a grease solvent, etching the printing areas of the plate slightly intaglio, depositing an ink receptive substance over the printing areas of the plate, and removing the light-hardened colloid from the non-printing areas of the plate.

6. A process of preparing intaglio lithographic plates from original plates or transfers, comprising, coating the entire plate with a solution of a light-sensitive mixture of glue and albumin, light-hardening the bichromated colloid over the surface of the entire plate, removing the ink and the light-hardened colloid overlying it from the vprinting areas of the plate by abrasion in the presence of moisture and a grease solvent, etching the printing areas of the plate slightly intaglio, depositing an ink receptive substance over the printing areas of the plate, and removing the light-hardened colloid froml the non-printing areas of the plate.

7. A process of preparing intaglio lithographic plates from original plates or transfers, comprising, coating the entire plate with a solution of a light-sensitive mixture of glue and another colloid, light-hardening the bichromated colloid over the surface of the entire plate, removing the ink and the light-hardened colloid overlying it from the printing areas of the plate by abrasion in the presence of moisture and a grease solvent,

etching the printing areas of theplate slightly intaglio, depositing an ink receptive substance over the printing` areas of the plate, and removing the light-hardened colloid from the non- `light-sensitive bichromated colloid, light-hardening the bichromated colloid over the surface ofthe entireplate, removing the vink and the light-hardened colloid voverlying it from the printing areas of- `the plate by abrasion in the presence of moisture and a grease solvent, etchthe printing areas ofthe'plate, and'removing the light-hardened vr'colloid from the non-printing areas of thelplate'wi'th a-'soluti'on of alkaline earth hydroxide' in water.

` [ROBERT F. Y .PAUL w. Doas'r. j v ANTHONY GEORGE. 

